1. Field of the Invention
The present invention relates to a method for producing a fiber laminate for holding liquid, a fiber laminate produced by the method, a liquid reservoir containing the fiber laminate, and a liquid-jetting head cartridge having the reservoir.
2. Description of the Related Art
In general, an ink tank (combined with a recording head or formed of a single replaceable tank) serving as a liquid reservoir for use in the field of liquid-jet recording (hereinafter also referred to as xe2x80x9cink-jet recordingxe2x80x9d) has a structure for controlling the force for holding liquid (used for recording; including a type containing a colored component, and a type containing no colored component and for acting on liquid containing a colored component so as to improve recording quality; hereinafter also simply referred to as xe2x80x9cinkxe2x80x9d) stored therein in order to properly supply the ink to a recording head for jetting liquid. This holding force is called xe2x80x9cnegative pressurexe2x80x9d because it serves to make the pressure at an ink discharge portion of the recording head negative relative to atmospheric pressure (a member for generating such negative pressure will be also referred to a xe2x80x9cnegative pressure generating memberxe2x80x9d).
The easiest method of generating such negative pressure is to use capillary force of an ink absorber, such as a urethane foam, provided inside the ink tank.
Japanese Patent Applications Laid-Open Nos. 7-125232 and 6-40043, to the same assignee, propose an ink tank including a liquid chamber using an ink absorber, in which the amount of ink to be contained per unit volume of the ink tank is increased, thereby obtaining a stable ink supply (this type of ink tank will be hereinafter referred to as a xe2x80x9ccombination ink tankxe2x80x9d because it includes both a chamber containing an ink absorber and a chamber containing ink).
FIGS. 6A and 6B are cross-sectional views showing the general configuration of a combination ink tank having the above-described structure, and showing how ink is consumed.
Referring to FIGS. 6A and 6B, the interior of an ink cartridge 10 is divided into two spaces by a partition 38 having a communication hole (communicating portion) 40. One of the spaces serves as a liquid chamber 36 enclosed excluding the communication hole 40 of the partition 38 so as to directly hold ink, and the other space serves as a negative pressure generating member containing chamber 34 for containing a negative pressure generating member 32. The negative pressure generating member containing chamber 34 is provided with an atmospheric air communicating portion (air communication port) 12 and a supply port 14 for supplying ink to a recording head (not shown). Ribs 42 are arranged between the negative pressure generating member 32 and the atmospheric air communicating portion 12, thereby forming a buffer space 44.
A supply tube on the recording head side is in pressure contact with the inside of the supply port 14, and an ink lead-out member 46 is also provided therein which has a greater capillary force and a higher physical strength than those of the negative pressure generating member 32 and which serves to properly lead ink out of the negative pressure generating member 32.
In such an ink tank configuration, when the ink in the negative pressure generating member 32 is consumed by the recording head, ink is supplied from the liquid chamber 36 to the negative pressure generating member 32 in the negative pressure generating member containing chamber 34 via the communication hole 40 of the partition 38, as shown in FIGS. 6A and 6B. In this case, the pressure in the liquid chamber 36 is reduced, whereas air taken from the atmospheric air communicating portion 12 via the negative pressure generating member containing chamber 34 enters the liquid chamber 36 through the communication hole 40 of the partition 38 (a state shown in FIG. 6B), thereby easing the pressure reduction in the liquid chamber 36. Therefore, even when ink is consumed by the recording head, ink from the liquid chamber 36 is filled into the negative pressure generating member 32 in accordance with the amount of consumption, and the negative pressure generating member 32 holds a constant amount of ink and maintains a substantially constant negative pressure with respect to the recording head. This stabilizes the supply of ink to the recording head.
Hitherto, a urethane foam has been often used as the above-described negative pressure generating member. The assignee of this application has proposed an ink tank in which a thermoplastic fiber material made of olefin resin is used as an absorber.
The fiber absorber is superior in ink wettability and utilization efficiency. The capillary force of the fiber absorber can be easily and arbitrarily set by changing fiber distance, fiber diameter, and the like.
For example, such a fiber may be thermoformed for use in the ink tank. Thermoforming permits fibers to be easily handled and to be easily inserted into the ink tank.
By thermoforming fiber packed in a die made of aluminum or the like, a fiber absorber of a required size can be formed. However, when heat is applied to the die having fiber therein, fiber is sometimes crushed down in the direction of gravity, depending on the conditions such as fiber density and dimensions. This seems to be because fiber having impact resilience is contained in close contact with the inside of the die before heating, whereas the impact resilience is reduced by melting of the contact portion of the fiber and a decrease in elasticity (a decrease in spring constant) of a base portion of the fiber with a temperature increase when heat is applied to the fiber, and the fiber is crushed by its own weight due to gravity.
FIGS. 7A, 7B, and 7C show a case in which a fibrous material laminate 1, constructed by a web stacked block (fibrous material stacked block) formed by stacking a plurality of webs (fibrous materials) with fibers oriented in almost the same direction, is inserted into an aluminum die in order to obtain a fiber laminate.
The fibers are oriented in a predetermined fiber direction xe2x80x9caxe2x80x9d and are stacked in a stacking direction xe2x80x9cbxe2x80x9d orthogonal to the fiber direction xe2x80x9caxe2x80x9d, as shown in FIG. 7A. The fibrous material laminate 1 is compressed in the stacking direction and packed in a die 2, and a cover 3 is put on the die 2, as shown in FIGS. 7B and 7C.
FIGS. 8A and 8B show a state in which the fibrous material laminate 1 packed in the die 2 is worked by an example of a thermoforming method.
In this example, when heat begins to be applied from an initial state in which the fibrous material laminate 1 is packed in the entirety of the die 2, the fibrous material laminate 1 is gradually crushed from its peripheral portion in the direction of gravity, as shown in FIG. 8A. This is because heat is conducted from the periphery of the die 2, and the influence of heat first acts on the peripheral portion of the fibrous material laminate 1. When further heat is applied, heat is conducted to the interior of the fibrous material laminate 1, as shown in FIG. 8B, and the entire bottom side of the fibrous material laminate 1 is crushed. In this case, since its own weight is laid on the fibrous material laminate 1, the density of the fibrous material laminate 1 differs between the upper part and the lower part in the direction of gravity. That is, the lower part of the fibrous material laminate 1, which is more strongly influenced by its own weight, has a high density, and the upper part has a low density, which produces a density gradient. While FIG. 8B shows two density areas of the fibrous material laminate 1, a low-density area and a high-density area, for simple illustration, in reality, the density gradient is continuously formed from the low-density area to the high-density area.
A product obtained by such thermoforming is referred to as a xe2x80x9cfiber laminatexe2x80x9d. In the fiber laminate, a density distribution differs between the upper part and the lower part, and a desired fiber density and a desired fiber size cannot be obtained. In a case in which the fiber laminate which has been removed from the die is cut into a desired size and the cut pieces are placed into ink tank housings so as to form ink tanks, the fiber density distribution varies among the cut pieces. Furthermore, it is substantially difficult to verify the differences in density distribution among the pieces in the cut state. As a result, one tank may have a high-density area on its bottom side in an operational state, and another tank may have a low-density area on its bottom side. This may cause undesirable retention and shortage of ink.
From a production viewpoint, it is not practical to thoroughly manage the processes from a thermoforming process for a fibrous material laminate to cut and insertion processes in order to avoid the above circumstances.
In particular, when the above-described fiber laminate is used as a negative pressure generating member in a combination ink tank having both a negative pressure generating member containing chamber and a liquid chamber, there is a fear that desired stability of ink supply will not be obtained.
For example, FIG. 9 is a schematic view showing a state that may be produced when a fiber laminate having a significantly nonuniform density is used as an ink absorber inside an ink tank, immediately before ink runs short inside the fiber laminate before a gas-liquid exchange operation. That is, fiber density is low in an area between a communication hole 40 and an ink supply port 14, and capillary force is insufficient. Therefore, ink does not lie in some sections. If ink supply is further continued from this state, ink in the liquid chamber and ink in an area communicating with the liquid chamber are not supplied, and ink supply is stopped at the time when ink in the fiber laminate at the supply port is entirely consumed, although ink still remains in the liquid chamber.
Such ink supply failure occurs not only in the ink tank having a configuration shown in FIG. 9, but also in ink tanks having no liquid chamber.
When thermoformed olefin fiber is used, the difference between the thermoforming temperature and the fiber melting point is very small and the influence of softening is great, in comparison with thermoforming of polyester fiber.
The present invention has been made to overcome the above problems, and it is an object of the present invention to provide a method of producing a fiber laminate in which a fiber laminate is prevented from being undesirably crushed downward in the direction of gravity during thermoforming, and in which the fiber laminate has a desired size, a desired fiber density state, and high ink wettability; a fiber laminate produced by the method; a liquid reservoir containing the fiber laminate and for stably supplying ink; and a liquid-jetting head cartridge having the liquid reservoir.
According to one aspect of the present invention, there is provided a fiber laminate production method in which fibrous materials oriented in almost the same direction are stacked and thermoformed, the production method including a step of controlling the influence of gravity on a laminate of the fibrous materials during thermoforming.
According to another aspect of the present invention, there is provided a fiber laminate produced by the above production method.
According to a further aspect of the present invention, there is provided a liquid reservoir for containing the fiber laminate produced by the method, and for holding liquid to be used in recording.
According to a further aspect of the present invention, there is provided a liquid-jetting head cartridge including the liquid reservoir, and a liquid-jetting head for jetting the liquid contained in the liquid reservoir.
By using the above production method, only a surface or a part of the heated fiber does not move down in the direction of gravity, and the fiber absorber is not likely to be influenced by gravity. Therefore, fiber is prevented from being crushed due to its own weight.
When the liquid reservoir or the liquid-jet head cartridge is constituted by the fiber absorber produced by the method in which only a part is not undesirably densified due to gravity, it is possible to reduce the amount of ink remaining in the reservoir and to stabilize ink supply performance.
Further objects, features, and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.